U.S. patent number 9,721,709 [Application Number 14/727,181] was granted by the patent office on 2017-08-01 for inductively decoupled dual smes in a single cryostat.
This patent grant is currently assigned to Novum Industria LLC. The grantee listed for this patent is Novum Industria LLC. Invention is credited to Alexey Radovinsky.
United States Patent |
9,721,709 |
Radovinsky |
August 1, 2017 |
Inductively decoupled dual SMES in a single cryostat
Abstract
Various SMES systems that include two magnets in a single
cryostat are disclosed. These dual SMES systems can be used, for
example, to provide uninterrupted power to a data center. The two
coil sets are arranged such that they are magnetically decoupled
from each other. In one embodiment, a toroidal coil set is used as
the primary coil set. The toroidal coil set has a plurality of
toroidal field (TF) coils extending radially outward and evenly
spaced in the circumferential direction. The second coil set may be
a solenoidal coil set having a main coil and a plurality of
shielding coils. The toroidal coil set may be disposed in the space
between the main coil and the shielding coils of the solenoidal
coil set. Alternate designs are also presented.
Inventors: |
Radovinsky; Alexey (Cambridge,
MA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Novum Industria LLC |
New York |
NY |
US |
|
|
Assignee: |
Novum Industria LLC (New York,
NY)
|
Family
ID: |
54770130 |
Appl.
No.: |
14/727,181 |
Filed: |
June 1, 2015 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20150357104 A1 |
Dec 10, 2015 |
|
Related U.S. Patent Documents
|
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
|
62007684 |
Jun 4, 2014 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F17C
3/085 (20130101); H01F 27/28 (20130101); H01F
6/04 (20130101); H01F 6/06 (20130101); F25D
3/102 (20130101); H02J 15/00 (20130101) |
Current International
Class: |
H01F
27/28 (20060101); H01F 6/06 (20060101); H01F
6/04 (20060101); F25D 3/10 (20060101); F17C
3/08 (20060101); H02J 15/00 (20060101) |
Field of
Search: |
;336/55-62,225,229 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
94/03910 |
|
Feb 1994 |
|
WO |
|
00/39815 |
|
Jul 2000 |
|
WO |
|
Other References
P Tixador, "SMES. Superconducing Magnetic Energy Storage,"
Presentation at the European Summer School on Superconductivity,
2011. cited by applicant .
Abdo A. Husseiny, Zeinab A. Sabri, "Air Force Superconductive
Magnetic Energy Storage (SMES) Requirements", Apr. 1993. cited by
applicant .
P. Tixador, "Superconducting Magnetic Energy Storage: Status and
Perspective," IEEE/CSC&ESAS European Supercon. News Forum, No.
3, Jan. 2008. cited by applicant .
International Search Report and Written Opinion mailed Dec. 21,
2015 in corresponding PCT application No. PCT/US15/33684. cited by
applicant.
|
Primary Examiner: Nguyen; Tuyen
Attorney, Agent or Firm: Nields, Lemack & Frame, LLC
Parent Case Text
This application claims priority of U.S. Provisional Patent
Application Ser. No. 62/007,684, filed Jun. 4, 2014, the disclosure
of which is incorporated herein by reference in its entirety.
Claims
What is claimed is:
1. A dual SMES system, comprising a first coil set and a second
coil set, arranged such that there is no mutual inductance between
the first coil set and the second coil set, wherein the first coil
set and the second coil set are disposed in one cryostat, wherein
the first coil set is a toroidal coil set and the second coil set
comprises a plurality of window frame racetracks with alternating
polarities, arranged around the first coil set.
2. A dual SMES system, comprising a first coil set and a second
coil set, arranged such that there is no mutual inductance between
the first coil set and the second coil set, wherein the first coil
set and the second coil set are disposed in one cryostat, wherein
the first coil set operates in persistent mode and the second coil
set is permanently online.
3. The dual SMES system of claim 2, wherein more of total magnetic
energy is stored in the first coil set than in the second coil
set.
4. A dual SMES system, comprising: a toroidal coil set; and a
solenoidal coil set, comprising a main coil and a plurality of
shielding coils arranged around the main coil; wherein the toroidal
coil set is disposed in a space between the main coil and the
shielding coils of the solenoidal coil set, and wherein the
toroidal coil set comprises a plurality of toroidal coils extending
radially outward, each toroidal coil comprising a plurality of
racetracks.
5. The dual SMES system of claim 4, wherein the toroidal coil set
and the solenoidal coil set are disposed in one cryostat.
6. The dual SMES system of claim 4, wherein 80% of total magnetic
energy is stored in the toroidal coil set.
7. A dual SMES system, comprising: a toroidal coil set; and a
solenoidal coil set, comprising a main coil and a plurality of
shielding coils arranged around the main coil; wherein the toroidal
coil set is disposed in a space between the main coil and the
shielding coils of the solenoidal coil set, and wherein 80% of
total magnetic energy is stored in the toroidal coil set.
Description
FIELD
Embodiments of the present disclosure relate to superconducting
magnetic energy storage systems (SMES), and more particularly, dual
SMES in a single cryostat.
BACKGROUND
Superconducting Magnets for Energy Storage (SMES) systems have high
potential for being used in various capacities for various
applications. Some applications require several energy storage
systems with different characteristics, such as the total stored
energy, discharge rate, mode of operation, etc. Each SMES installed
in its individual cryostat requires a cooling system and the
magnets have to be installed at some distance, in order to minimize
the inductive coupling via their respective stray magnetic fields,
which can have a negative effect on their performance.
It would be advantageous if it were possible to combine two or more
SMES magnets in a single cryostat. Combining several SMES magnets
in one cryostat can result in substantial savings both in the cost
of the equipment and in the space requirements for its
installation.
SUMMARY
Various SMES systems that include two coil sets in a single
cryostat are disclosed. These dual SMES systems can be used, for
example, to provide uninterrupted power to a data center. The two
coil sets are arranged such that they are magnetically decoupled
from each other. In other words, there is no mutual inductance
between the two coil sets. In one embodiment, a toroidal coil set
is used as the primary coil set. The toroidal coil set has a
plurality of toroidal field (TF) coils extending radially outward
and evenly spaced in the circumferential direction. The second coil
set may be a solenoidal coil set having a main coil and a plurality
of shielding coils. The toroidal coil set may be disposed in the
space between the main coil and the shielding coils of the
solenoidal coil set. Alternate designs are also presented.
BRIEF DESCRIPTION OF THE FIGURES
For a better understanding of the present disclosure, reference is
made to the accompanying drawings, which are incorporated herein by
reference and in which:
FIGS. 1A-1B show conventional toroidal coils that may be used with
the dual SMES according to one embodiment of the present
disclosure;
FIG. 2A depicts the mid-plane cross section of a single racetrack
assuming constant current densities;
FIG. 2B depicts discretization of the current distribution shown in
FIG. 2A;
FIG. 3A is a coil set comprised of N=16 toroidal coils;
FIG. 3B depicts a histogram of the magnetic field at the axial
cross section of the coil set of FIG. 3A;
FIG. 4A is a solenoidal magnetic system;
FIG. 4B depicts a histogram of the magnetic field at the axial
cross section of the coil set of FIG. 4A;
FIG. 5A shows a combined system employing the coil set of FIG. 3A
and FIG. 4A;
FIG. 5B depicts a histogram of the magnetic field at the axial
cross section of the magnet of FIG. 5A; and
FIGS. 6A-6C depict a sample schematic of an alternative inductively
decoupled dual SMES.
DETAILED DESCRIPTION
In some embodiments, this disclosure is directed to multiple SMES
systems used in the data centers. There are several functions that
can be served by SMES systems in the electrical power system of a
data center. However, it is noted that the multiple SMES described
herein can be used for other applications as well.
One attractive application is using SMES for providing an
Uninterrupted Power Supply (UPS) of the data processing equipment
in case of a power failure of the general electrical grid. Local
power generators incorporated in the power supply system can
provide continuous power supply for quite a long time. However,
some time is required to start these generators and to bring their
output to the required steady-state level. A primary, high energy
capacity, SMES can supply the power during this transitional
period. Since this is a very rare event, it is convenient to run
this SMES in a persistent mode. This minimizes the cooling
requirements by removing the current leads from the current path
during the idle time. The downside of this feature is that a very
short but still finite time is required to switch the SMES from the
persistent mode to the working condition and to start supplying the
equipment with the electrical power from this SMES.
A secondary, smaller capacity, SMES staying online permanently, can
bridge this time gap and will provide the power while the primary
SMES goes online. The same secondary SMES can be used continuously
to facilitate power conditioning of the grid signal resulting from
various voltage spikes and instabilities.
General requirements to the magnet configurations used for SMES
include high Specific Energy defined as the Stored Magnetic Energy
per unit Weight of the Superconductor and good field containment
resulting in safely low stray magnetic fields in the vicinity of
the magnet. Those skilled in the art are aware of magnetic
topologies that can satisfy these requirements to some extent.
Mechanical and cost-related considerations also apply. They are not
addressed in this proposal, which is limited to considering only
magnetic designs of some dual SMES options.
Constant Field Toroidal Magnet
One of the more traditional configurations of a SMES magnet is a
toroidal coil. Typically, this design is given preference over
other magnet topologies because it provides the best field
containment and, consequently, the highest density of the magnetic
field and a very low level of stray fields, even at small distances
from the magnet.
The main drawback of the conventional toroidal magnets comprised of
multiple racetrack-shaped coils is the inverse relationship between
magnetic field and the radius, r. This results in a distribution of
the magnetic field that peaks up at the outer side of the inner leg
of the racetrack and then decays as 1/r, resulting in rather
inefficient space utilization.
To mitigate this disadvantage, a toroidal magnet comprised of
discrete graded coils creating an almost constant magnetic field in
a large volume inside the magnet may be used on one embodiment.
Originally, "alternative toroid" design was defined in terms of a
1D axisymmetric radial function of non-uniform current density
distribution. In the present disclosure, this distribution is
discretized both azimuthally and radially to be represented by a
multiplicity of conventional racetracks as shown in FIGS. 1A and
1B. This discretization leads to a more convenient for
implementation constant current density distribution.
Consider a coil system comprised of N Toroidal Field (TF) coils
extending radially outward and evenly spaced in the circumferential
direction. FIGS. 1A and 1B depict a magnet 10 having N=16 TF coils
11 and a view of a single TF coil 11, respectively. Each TF coil 11
is comprised of multiple racetracks 12 arranged as described
below.
The straight legs of the racetracks 12, which are parallel to the
axis of the magnet 10, are arranged for the best compliance with
the current distribution shown in the schematics in FIGS. 2A and
2B. FIG. 2A depicts the mid-plane cross section of a single
racetrack 12 assuming constant current densities.
In FIG. 2A, W is the width of the racetrack winding. Rin and Rout
are radial boundaries, where R0=Rin+h0. There are four segments;
which are h0, hk, h1 and h0 long, respectively. Current flows in a
direction that is normal to the page. Respective current densities
in the segments are j0, jk, j0 and j0, those marked by (+) are
opposite to those marked by (-). Lengths (h0, hk, h1) and current
densities (j0, jk) are scaled so that the total current in all bars
is an algebraic zero.
The following parameters are given: B0--maximum target field in the
system; j0--current density in segments 1, 3 and 4; N--rotational
symmetry of the system; Rout--outer radial limit of the coils;
Lc--axial extent of the coils (in z-direction); W--width of the
coil; and dRin--see below.
System parameters may be calculated by the following procedure: 1.
Rmin=W/2*Cot(.pi./N), wherein Rmin is the minimum radial position
of the coil to avoid overlapping in the left corners in FIG. 2A; 2.
Rin=Rmin+dRin--actual radial position where the coils begin,
dRin.gtoreq.0 is a parameter of choice; 3. h0=Rin*k/(1-k), where
k=2*B0/(.mu..sub.0*N*W*j0); 4. R0=Rin+h0, wherein R0 is the outer
radial limit of segment 1; and 5. jk=k*j0, where jk is the current
density in segment 2 6. hk=(Rout-R0-h0)/(1+k), h1=k*hk are the
radial extents of segments 2 and 3, respectively.
FIG. 2B depicts discretization of the current distribution shown in
FIG. 2A. Segments 1 and 4 represent the opposite legs of the main
racetrack. Segments 2 and 3 are broken up into equal numbers, m, of
current legs of the inner racetracks, each with the same current
density, j0. Discrete currents in Segment 2 are spaced evenly to
better match the uniformity of jk.
Coil Set A
Assume that a high energy capacity toroidal magnet (referred to as
Coil set A 20) is to be the primary SMES. The magnet, coil set A
20, shown in FIG. 3A, is comprised of N=16 toroidal coils 21. The
magnetic field of Coil set A 20 is contained in a toroidal volume.
FIG. 3B depicts a histogram of the magnetic field at the axial
cross section of Coil set A 20. Fringe fields outside the high
constant field area are very small.
Coil Set B
The desired properties of the secondary SMES are: 1. it has to be
magnetically decoupled from the primary magnet, and 2. it has to
have relatively small fringe fields.
A solenoidal magnetic system (Coil set B) shown in FIG. 4A is one
of the topologies satisfying both requirements. Coil set B 30 is
comprised of the main coil 31, a big solenoid forming the core of
the magnet, and multiple shielding coils 32. The shielding coils 32
are larger radius and smaller cross section solenoids with current
moving in the direction opposite to that of the current in the main
coil 31. Most of the magnetic field of Coil set B 30 is contained
in a cylindrical volume inside the main coil 31. FIG. 4B depicts a
histogram of the magnetic field at the axial cross section of Coil
set B 30. Currents in the Main coil 31 and in the Shielding Coils
32 are selected so that the fringe field outside the magnet 30 is
safely low. The poloidal field in the cylindrical space between the
Main coil 31 and the Shielding coils 32 is much smaller than inside
the Main coil 31.
Coil Set A+B
A combined or dual SMES system (Coil set A+B 40), comprised of two
magnets, one formed by Coil set A 20 and the other by Coil set B
30, installed in one cryostat is a good candidate for being used in
the data centers. An example of this combined system 40 is shown in
FIG. 5A. The toroidal Coil set A 20 is conveniently installed in
the free space between the Main coil 31 and the Shielding coils 32
of Coil set B 30. Operating currents in Coil set A 20 and Coil set
B 30 are scaled so that the peak fields on the superconductors in
each of these are set to the respective safe values defined by the
magnetic design. FIG. 5B depicts a histogram of the magnetic field
at the axial cross section of Coil set A+B 40. In this particular
design, currents in the magnets of Coil sets A and B are scaled so
that the maximum fields in the high field volumes of both Coil sets
are the same.
Each of the coil system A 20 and the coil system B 30 forms its own
independent power circuit. Coils of each of the subsystems are
connected in series forming respective circuits A and B. Though
individual coils of circuits A and B are inductively coupled,
circuits A and B are fully decoupled, i.e. the magnetic flux of
Coils A integrated over circuit B is always zero, and vice
versa.
Since the mutual inductance between the decoupled Coil sets A and B
is zero, the following law is characteristic of a dual SMES. At a
working point E.sub.A+B, magnetic energy stored in Coil set A+B, is
an exact sum of respective magnetic energies, E.sub.A and E.sub.B,
stored in Coil sets A and B, measured when the current in the other
Coil set is zero, E.sub.A+B=E.sub.A+E.sub.B (1) In the particular
case depicted in FIG. 5A, energies, E.sub.A and E.sub.B, comprise
exactly 80% and 20% of E.sub.A+B, respectively. In other
embodiments, the energy in Coil set A is more than the energy
stored in Coil Set B. In some embodiments, the Coil set A is in
persistent mode, while Coil set B is permanently online.
Alternative Designs
Note that other options for the topology of the primary and
secondary magnet systems of a magnetically decoupled dual SMES are
possible. The common characteristic of these topologies is that the
mutual inductance between the primary and the secondary Coil sets
is zero and consequently the balance of stored energies defined by
formula (1) is valid. FIGS. 6A-6C depict a sample schematic of an
alternative SMES 50, in which a toroidal Coil set A' 51 is
complemented by Coil set B' 52, comprised of window-frame
racetracks 53 with alternating polarities. The coils are positioned
so that mutual inductance between electrical circuits formed by
connected in series coils of Coil sets A' 51 and coils of Coil set
B' 52 is zero.
The present disclosure is not to be limited in scope by the
specific embodiments described herein. Indeed, other various
embodiments of and modifications to the present disclosure, in
addition to those described herein, will be apparent to those of
ordinary skill in the art from the foregoing description and
accompanying drawings. Thus, such other embodiments and
modifications are intended to fall within the scope of the present
disclosure. Furthermore, although the present disclosure has been
described herein in the context of a particular implementation in a
particular environment for a particular purpose, those of ordinary
skill in the art will recognize that its usefulness is not limited
thereto and that the present disclosure may be beneficially
implemented in any number of environments for any number of
purposes. Accordingly, the claims set forth below should be
construed in view of the full breadth and spirit of the present
disclosure as described herein.
* * * * *